Network slice selection

ABSTRACT

Network nodes and methods for control thereof for dynamic network slice selection. An AMF receives a UE request originating from the UE, the UE request being any one of a registration request and a session request. A network slice requester controls a transmitter to transmit a network slice selection request to a PC_NSS. A selection data manager of the PC_NSS determines selection data specifying one or more UE specific parameters affecting network slice selection. A network slice selector selects a network slice assignable for the UE, based on the selection data, determines network slice data and a corresponding network slice routing rule, and transmits them to the AMF. A network slice manager of the AMF controls assignment of a network slice to the UE in dependence on the received network slice data and network slice routing rule.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Submission Under 35 U.S.C. § 371 for U.S. NationalStage Patent Application of International Application Number:PCT/EP2016/082939, filed Dec. 30, 2016 entitled “NETWORK SLICESELECTION,” the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to the selection of network slices in atelecommunications network for use by a User Equipment (UE).Specifically, exemplary methods and apparatus relate to dynamicselection of network slices in a telecommunications network.

BACKGROUND

A network slice is a logical network serving a defined business (ornetwork) purpose or a specific customer. A network slice includes allthe required network resources to put the network slice into effect andis created, changed and removed by management functions within thetelecommunications network.

A network slice is complete in the context of that network or end-to-endpurpose, i.e. they are and behave like networks in their own right,including all the required capabilities and resources. This extends allthe way from the share of the infrastructure resources, throughconfigured network functions to network management or even OperationSupport Systems (OSS) and/or Business Support System (BSS) capabilitiesand encompasses both mobile and fixed network access.

Just as existing networks are built to realize services, so are networkslices. Network slices are not services in themselves, but they arebuilt to realize one or several services. As a special case, a service(or instance thereof) may map one-to-one with a network slice, allowing,for example, wholesale type services. For the sake of clarity, the term‘service’ may represent a generic service, e.g. an Online Bankingservice, whereas the term ‘service instance’ may represent a specificservice, such as e.g. an Online Banking service in a specific bank oreven a specific transaction carried out in an Online Banking.

As slices can be created to address a new business or networkrequirement or customer and may need to adapt to changes, they requirenew types of life cycle management functions, which have the role ofcreating, changing (e.g. upgrading) or removing network slices.

Network slicing is a relatively new paradigm or way of viewing anddesigning the end-to-end provider network.

The Third Generation Partnership Project (3GPP) standard is currentlydefining a new system architecture for next generation mobile networksthat will be the next major phase of mobile telecommunication standardsbeyond the current 4^(th) Generation (4G). The new architecture is beingstudied in the 3GPP TR 23.799 and an exemplary architecture discussed in3GPP TR 23.799, for a non-roaming scenario, can be seen in FIG. 1.

The architecture shown in FIG. 1 includes the logical entities (ornetwork functions) that will replace/evolve from the current 4G definedlogical entities. For example, the mobility management tasks currentlybeing performed by the Mobility Management Entity (MME) will be assumedby the Next Generation Access and Mobility Management Function (AMF, orMMF) plus additional tasks required in a 5G evolved network. In asimilar way, the Packet Data Network Gateway (PGW) responsibilities canbe assumed by the Next Generation Session Management Function (SMF, orSMF) and Next Generation Core User Plane (UP) functions in addition tonew functionality required in a 5G evolved network.

The roles of the logical entities in FIG. 1 and the associatedinterfaces are being studied and defined in the 3GPP TR 23.799. It isnoted that the terminology is being adapted during the development of3GPP TR 23.799. Accordingly, within the scope of this document theentities “MMF” and “AMF” might be considered equivalent. In a similarway, the entities “SDM” and “UDM” might be considered equivalent. Therequirements that the architecture must fulfill are described in clause4.1 of TR 23.799. One of the defined requirements relates to “NetworkSlicing”.

Network slicing enables the operator of a network to create networkscustomized to provide optimized solutions for different market ornetwork scenarios which demand diverse requirements, e.g. in the areasof functionality, performance and isolation. The network slice is thus alogical representation of Network Functions (NF) and their correspondingresource requirements necessary to provide the requiredtelecommunication services and network capabilities within theirresponsibility.

The 3GPP specified, in Release 13, the support of multiple DedicatedCore Networks (DCN) within a Public Land Mobile Network (PLMN), each ofthese DCNs including one or a plurality of Core Network Nodes. Each DCNmay be dedicated to serving specific types of subscribers and fordifferent motivations, e.g. to provide DCNs with specificcharacteristics/functions for scaling, to isolate specific UEs orsubscribers (e.g. Machine-to-Machine (M2M) characteristics/functions orscaling, subscribers belonging to a specific enterprise or separateadministrative domain, etc.). Further information on this is included in3GPP TS 23.401. Herein, when we refer to a “CN Instance” this termencompasses a DCN.

3GPP TR 23.799 identifies different alternatives to cope with networkslicing and how they relate to CN Instances (see clause 6.1 and AnnexD). According to the studied proposals, there can be common NetworkFunctions that apply to every network slice and specific NetworkFunctions that are applicable in the context of a network slice.

In order to realize network slicing, 3GPP TR 23.799 14.0.0, Annex D,defines three groups of solutions for the support of multiple networkslices per UE:

-   -   Group A, represented in FIG. 2a and where a UE 200 a obtains        services through a shared access network 202 a and from        different network slices 204 a, 206 a and different CN        instances, each CN instance containing all the NFs required for        the service. This group is characterized by independent        subscription management/mobility management for each network        slice.    -   Group B, represented in FIG. 2b and in which a UE 200 b obtains        services through a shared access network 202 b and from        different network slices 204 b, 206 b, but that assumes some NFs        208 b are common between the network slices, while other        functions reside in their individual network slices 204 b, 206        b.    -   Group C, represented in FIG. 2c and in which a UE 200 c obtains        services through a shared access network 202 c and assumes that        the control plane 204 c handling is common between the slices,        while the user plane(s) 206 c, 208 c are handled as different        network slices.

According to the agreements reached at the time of writing, Group B typeis the preferred solution. Group C is considered subsumed under Group B.Group A is likely not to be pursued.

According to the current procedures defined in 3GPP TR 23.799, a NetworkSlice Selection function (NSSF) is responsible for selecting a networkslice for a UE and is only aware of the network slice identity allocatedto a UE, the subscription information for the user of the UE and localpolicies. Based on that information, it could be possible according tosome of the solutions described in 3GPP TR 23.799 to reselect anothernetwork slice for a UE if network or other conditions change. Thenetwork slice identity known by the NSSF may be mapped into theapplicable NFs that form the network slice based on configuration.

This type of solution is very sensitive to changes (e.g. the definitionof a new network slice, or the redefinition of the existing one). As thenumber of network slices grows, a large computational overhead isrequired for configuration of the NFs and the possibility of changingentities in a dynamic way is reduced. The NFs would need to know:whether they are common NFs or if they are network slice specific NFs;the set of network slices they are to be used within; and, in order toroute PDU session establishment and Protocol Data Unit (PDU) sessionestablishment, the set of NFs to be used in each network slice.

The selection of network slices can be performed as part of differentprocedures, e.g. during attach and at PDU session establishment. Thefollowing list includes some examples of use cases that would be limitedor be highly impacted with the current proposed solutions due to thelimitations in the way network slices are being defined:

-   -   Allocating heavy users to a specific network slice where they        compete for resources with other heavy users.    -   Allocating high signalling load terminals (malfunctioning        terminals) to a specific network slice where they compete for        resources with other high signalling load terminals.    -   Allocating different network slices for different services (e.g.        Voice Over Long Term Evolution (VoLTE) and Mobile Broadband        (MBB)) or for a same service, e.g. VoLTE, depending on        additional criteria such as, for example, location, time of day,        congestion situation etc.

According to current solutions, the UE, the NFs and the NSSF need toknow how to treat the network slice identifier. This identifier shouldhave information (or refer to that information) related to the entitiesthat form the network slice and how to address each of them (when otherinformation included in the UE request such as, for example, the AccessPoint Name (APN), is not enough). This information is staticallyconfigured in the affected logical entities, making the use casesdescribed above quite static, and badly scalable, as all the decisionsrelated to the network slice definition need to be taken in advance.

SUMMARY

The inventors have realised that the market for telecommunicationsnetworks will evolve and network operators will demand more flexibilityand adaptability to the network to implement their and their partners'business goals. In this short-medium term context, the inventors haveappreciated that the implementation of efficient mechanisms that allowthe dynamic allocation of a UE to different network slices provides anattractive enabler for the dynamic creation and availability of networkslices based on changing conditions.

The inventors have appreciated that current mechanisms do not considerthat a reselection of the network slice can be required in a dynamic way(e.g. considering measured conditions under which the service the UE isaccessing is being delivered).

According to an aspect of the invention, there is provided a networknode configured for use as an Access and Mobility Management Function,AMF, of a telecommunications network, the AMF for controlling networkslice assignment to a user equipment, UE, within the telecommunicationsnetwork. The network node comprises a receiving means, which may be areceiver, configured to receive a UE request originating from the UE,the UE request being any one of a registration request and a sessionrequest. The network node comprises a network slice requesting means,which may be a network slice requester, configured to control atransmitter to transmit a network slice selection request to a PolicyControl Network Slice Selection function, PC_NSS. The receiver isconfigured to receive, from the PC_NSS, network slice data identifying anetwork slice assignable for the UE, and a corresponding network slicerouting rule identifying the assignable network slice and a set ofnetwork functions forming the assignable network slice. The network nodecomprises a network slice managing means, which may be a network slicemanager, configured to control assignment of a network slice to the UEin dependence on the received network slice data and network slicerouting rule.

In particular, the registration request may correspond to, for example,an access request or a UE request for network connection during anattach procedure. Also in particular, the session request may correspondto e.g. a UE request for establishment of a PDU session.

Optionally, the network slice manager is configured to determine whetherthe assignable network slice identified by the received network slicedata is supported by the AMF, and further configured: if the assignablenetwork slice is not supported by the AMF, to control the transmitter totransmit the UE request to a further AMF for control of assignment of anetwork slice for the UE; and if the assignable network slice issupported by the AMF, to assign the assignable network slice for the UE.

Optionally, the network slice data received via the receiver comprisesan authorized network slice selection assistance information, NSSAI,representing one or more assignable network slices for the UE, andrespectively corresponding one or more network slice routing rules.

Optionally, each network slice routing rule further identifies a servicescope at which the assignable network slice applies, wherein the servicescope indicates any one of: a service, a service in a packet datanetwork, PDN, and a service data flow in a PDN.

Optionally, the network slice manager is configured to determine anapplicable network slice to be assigned for the UE, amongst the one ormore assignable network slices, based on the service scope identified byeach network slice routing rule.

Optionally, the receiver is further configured to receive a UE-providedNSSAI along with the UE request.

Optionally, the network slice manager is configured, if the UE-providedNSSAI matches the authorized NSSAI, to enforce the network slice routingrule for the UE-provided NSSAI or, if the UE-provided NSSAI does notmatch the authorized NSSAI, to enforce the network slice routing rulefor the authorized NSSAI.

Optionally, the network slice routing rule further comprises dataindicating one or more conditions and/or events specifying when afurther network slice selection request should be transmitted to thePC_NSS.

Optionally, upon the receiver receiving a further UE request originatingfrom the UE, the network slice requester is configured to determinewhether one or more of the conditions and/or events has occurred, and,if so, to control the transmitter to transmit a further network sliceselection request to the PC_NSS.

Optionally, the network slice manager is configured to control thetransmitter to transmit the data indicating one or more conditionsand/or events to a Session Management Function, SMF.

According to an aspect of the invention, there is provided a method forcontrolling a network node configured for use as an Access and MobilityManagement Function, AMF, of a telecommunications network, the AMF forcontrolling network slice assignment to a user equipment, UE, within thetelecommunications network. The method comprises receiving, by areceiver, a UE request originating from the UE, the UE request being anyone of a registration request and a session request. The methodcomprises controlling a transmitter, by a network slice requester, totransmit a network slice selection request to a Policy Control NetworkSlice Selection function, PC_NSS. The method comprises receiving, by thereceiver from the PC_NSS, network slice data identifying a network sliceassignable for the UE, and a corresponding network slice routing ruleidentifying the assignable network slice and a set of network functionsforming the assignable network slice. The method comprises controlling,by a network slice manager, assignment of a network slice to the UE independence on the received network slice data and network slice routingrule.

Optionally, the method further comprises determining, by the networkslice manager, whether the assignable network slice identified by thereceived network slice data is supported by the AMF: if the assignablenetwork slice is not supported by the AMF, the network slice managercontrolling the transmitter to transmit the UE request to a further AMFfor control of assignment of a network slice for the UE; and if theassignable network slice is supported by the AMF, the network slicemanager assigning the assignable network slice for the UE.

Optionally, the network slice data received via the receiver comprisesan authorized network slice selection assistance information, NSSAI,representing one or more assignable network slices for the UE, andrespectively corresponding one or more network slice routing rules.

Optionally, each network slice routing rule further identifies a servicescope at which the assignable network slice applies, wherein the servicescope indicates any one of: a service, a service in a packet datanetwork, PDN, and a service data flow in a PDN.

Optionally, the method further comprises determining, by the networkslice manager, an applicable network slice to be assigned for the UE,amongst the one or more assignable network slices, based on the servicescope identified by each network slice routing rule.

Optionally, the method further comprises receiving, by the receiver, aUE-provided NSSAI along with the UE request.

Optionally, the method further comprises, if the UE-provided NSSAImatches the authorized NSSAI, enforcing by the network slice manager(318) the network slice routing rule for the UE-provided NSSAI or, ifthe UE-provided NSSAI does not match the authorized NSSAI, enforcing bythe network slice manager the network slice routing rule for theauthorized NSSAI.

Optionally, the network slice routing rule further comprises dataindicating one or more conditions and/or events specifying when afurther network slice selection request should be transmitted to thePC_NSS.

Optionally, upon the receiver receiving a further UE request originatingfrom the UE, the method further comprises determining, by the networkslice requester, whether one or more of the conditions and/or events hasoccurred, and, if so, controlling the transmitter to transmit a furthernetwork slice selection request to the PC_NSS.

Optionally, the method further comprises controlling, by the networkslice manager, the transmitter to transmit the data indicating one ormore conditions and/or events to a Session Management Function, SMF.

According to an aspect of the invention, there is provided a networknode configured for use as a Policy Control Network Selection function,PC_NSS, of a telecommunications network, the PC_NSS for selecting one ormore network slices assignable for a UE within the telecommunicationsnetwork. The network node comprises a receiving means, which may be areceiver, configured to receive a network slice selection request froman Access and Mobility Management Function, AMF. The network nodecomprises a selection data managing means, which may be a selection datamanager, configured to determine selection data specifying one or moreUE specific parameters affecting network slice selection. The networknode comprises a network slice selecting means, which may be a networkslice selector, configured to select a network slice assignable for theUE, based on the selection data, and to determine network slice dataidentifying the assignable network slice and a corresponding networkslice routing rule identifying the assignable network slice and a set ofnetwork functions forming the assignable network slice. The networkslice selector is further configured to control a transmitter totransmit to the AMF the network slice data and the corresponding networkslice routing rule for controlling assignment of a network slice for theUE based on the network slice data and network slice routing rule.

Optionally, the network slice data transmitted via the transmittercomprises an authorized network slice selection assistance information,NSSAI, representing one or more assignable network slices for the UE,and respectively corresponding one or more network slice routing rules.

Optionally, each network slice routing rule further comprises a servicescope at which the assignable network slide applies, wherein the servicescope indicates any one of: a service, a service in a packet datanetwork, PDN, and a service data flow in a PDN.

Optionally, the network slice routing rule further comprises dataindicating one or more conditions and/or events specifying when afurther network slice selection request should be transmitted to thePC_NSS.

Optionally, the network slice selector is further configured to controlthe transmitter to transmit to the AMF redirect data for redirectingassignment of the network slice for the UE to a further AMF, and whereinthe network slice selector is configured to determine the redirect databased on whether the assignable network slice is supported by the AMF.

Optionally, the selection data manager is configured to determine atleast part of the selection data by controlling the transmitter totransmit one or more selection data requests to one or more furthernetwork nodes in the telecommunications network, and wherein thereceiver is configured to receive the selection data from the one ormore further network nodes.

Optionally, the selection data further comprises: network slice datacomprising one or more network slice attributes affecting network sliceselection, the time of day and/or one or more network operator specifiedconditions.

According to an aspect of the invention, there is provided a method forcontrolling a network node configured for use as a Policy ControlNetwork Selection function, PC_NSS, of a telecommunications network, thePC_NSS for selecting one or more network slices assignable for a UEwithin the telecommunications network. The method comprises receiving,by a receiver, a network slice selection request from an Access andMobility Management Function, AMF. The method comprises determining, bya selection data manager, selection data specifying one or more UEspecific parameters affecting network slice selection. The methodcomprises selecting, by a network slice selector, a network sliceassignable for the UE, based on the selection data, and determining, bythe network slice selector, network slice data identifying theassignable network slice and a corresponding network slice routing ruleidentifying the assignable network slice and a set of network functionsforming the assignable network slice. The method comprises controlling atransmitter, by the network slice selector, to transmit to the AMF thenetwork slice data and the corresponding network slice routing rule forcontrolling assignment of a network slice for the UE based on thenetwork slice data and network slice routing rule.

Optionally, the network slice data transmitted via the transmittercomprises an authorized network slice selection assistance information,NSSAI, representing one or more assignable network slices for the UE,and respectively corresponding one or more network slice routing rules.

Optionally, each network slice routing rule further comprises a servicescope at which the assignable network slide applies, wherein the servicescope indicates any one of: a service, a service in a packet datanetwork, PDN, and a service data flow in a PDN.

Optionally, the network slice routing rule further comprises dataindicating one or more conditions and/or events specifying when afurther network slice selection request should be transmitted to thePC_NSS.

Optionally, the method further comprises controlling, by the networkslice selector, the transmitter to transmit to the AMF redirect data forredirecting assignment of the network slice for the UE to a further AMF,and determining, by the network slice selector, the redirect data basedon whether the assignable network slice is supported by the AMF.

Optionally, the method further comprises determining, by the selectiondata manager, at least part of the selection data by controlling thetransmitter to transmit one or more selection data requests to one ormore further methods in the telecommunications network, and receiving,by the receiver, the selection data from the one or more further networknodes.

Optionally, the selection data further comprises: network slice datacomprising one or more network slice attributes affecting network sliceselection, the time of day and/or one or more network operator specifiedconditions.

According to an aspect of the invention, there is provided a computerprogram comprising instructions which, when executed on at least oneprocessor, cause the at least one processor to carry out any methoddisclosed herein.

According to an aspect of the invention, there is provided a carriercontaining the computer program mentioned above, wherein the carrier isone of an electronic signal, optical signal, radio signal, ornon-transitory computer readable storage medium.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block schematic representation of an exemplarytelecommunications network;

FIGS. 2a-c show block schematic representations, each of a group ofnetwork slicing configurations;

FIG. 3 is a block schematic representation of a network nodeimplementing a Mobility Management Function or Access MobilityManagement Function;

FIG. 4 is a block schematic representation of a network nodeimplementing a Policy Control for Network Slice Selection function;

FIG. 5 is a signalling diagram showing a method for network sliceselection; and

FIG. 6 is a signalling diagram showing a method for network sliceselection.

DETAILED DESCRIPTION

Methods and apparatus disclosed herein include mechanisms implemented ina core network node called Policy Control for Network Slice Selectionfunction (PC_NSS) that extends the network slice selection functionalitydescribed in 3GPP.

In exemplary methods and apparatus, in order to decide about whichnetwork slice to assign to a UE, the PC_NSS may access up to datenetwork slice parameters relating to a network slice for the servicethat the network slice is intended to deliver, the businesspurpose/customer that the network slice is serving, and/or the networkslice status. Network slice parameters may comprise, for example, loadwithin the network slice, current latency to deliver the intendedservice within the network slice, message loss within the network sliceetc.

For example, a 60% load in a network slice for MBB services in anEnterprise Business purpose might qualify the network slice as“available” and the PC_NSS may therefore determine that the networkslice can be assigned to the corresponding UE. Alternatively, given thesame load for a low latency application, such as for a GamingX networkuser, the PC_NSS might qualify the network slice as “latency_risk” anddetermine that it may not be assigned to the corresponding UE.

To instruct a core network node about how to route access or PDU sessionestablishment requests in a selected network slice, the PC_NSS maytransmit to the requesting network function (e.g. an MMF/AMF or SMF) aNetwork Slice Routing Rule (NSRR).

A Network Slice Routing Rule may include one or more of the followingper network slice:

-   -   the network slice instance ID;    -   the service scope at which the network slice applies (e.g. any        service, any service in a Packet Data Network (PDN), a Service        Data Flow in a PDN);    -   the set of NFs (common and specific for the network slice)        selected to route the UE request, e.g. a PDU session        establishment request; and    -   one or more network slice selection events that trigger a        network slice reselection for each NF specified in the route        above. For example, the NSRR may specify that, in the AMF, a        request for network slice selection occurs at specific mobility        events and/or PDN connection requests. In a further example, the        NSRR may specify that the SMF should request network slice        selection (for further UP NF selection) at reception of a PDN        connection request. Other examples are possible.

For the sake of simplicity, any one of the AMF and MMF may beindistinctly referred to hereinafter to represent any one of them.

Exemplary methods and apparatus disclosed herein may be based on one ormore of the following features:

-   -   The PC_NSS, at policy decision request from the AMF as part of        the attach (or UE connectivity) procedure, and based on dynamic        policies, may select network slice(s) that can be assigned to        the UE at attach and at PDN connection establishment procedures.        If the selected network slice for the attach procedure does not        correspond with the one provided by the UE (the network slice(s)        provided by the UE may be derived by the PC_NSS from the Network        Slice Selection Assistance Information (NSSAI)), and the        selected network slice does not comprise as NFs the AMF        requesting policy decision, the AMF may redirect the UE to the        proper network slice, and may return the determined NSSAI. The        AMF may inform the UE about the new NSSAI.    -   When the selected network slice corresponds to the one derived        by the NSSAI provided by the UE, or the requesting AMF is a        network function included into the selected network slice(s),        the PC_NSS may provide to the AMF at UE attach the information        about the NSRR(s) (multiple NSRRs when the UE can simultaneously        access to several slices).    -   At PDU session establishment, the AMF may select an applicable        network slice assignable for the UE and may apply the        correspondingly applicable NSRR and at service scope matching,        it may either contact the PC_NSS (if NSRR defined events for AMF        indicate to do so) or it may contact the SMF as indicated by the        set of NFs in the NSRR. When forwarding the PDU session        establishment to the SMF, the AMF may also include information        about whether the SMF has to contact the PC_NSS upon PDU session        establishment and may also include information about the UPF to        be selected.    -   The SMF may contact the PC_NSS at PDU session establishment if        the AMF indicated to do so. The PC_NSS may provide to the SMF        information about the NSRR to be applied for that network slice        to use at the service scope, e.g. service (data flow)        procedures. This decision may be based on dynamic polices that        consider different network and subscriber conditions. The PC_NSS        may also provide additional information to the SMF that        indicates under which conditions it needs to be triggered for        network slice re-evaluation.    -   The SMF, the AMF, or the MMF may contact the PC_NSS at other        events than attach/connectivity request or PDU session        establishment (such as mobility, change of access type, service        detection, etc.), if configured to do so within the NSRR. The        PC_NSS may then select a different network slice and/or provide        new NSRR(s). This enables use cases where an operator of the        network applies a different network slice for different        geographical areas, for different access networks or when a new        service is activated for this PDN connection.    -   The PC_NSS may modify or revoke any of the previously provided        NSRRs at any moment.    -   The PC_NSS can interface with an Analytics function, which is        configured to provide the PC_NSS with analytics insights (for        example, congested area, terminal malfunctioning, network slice        conditions) to be considered in the network slice selection        process. If a user starts a service that requires specific        latency requirements and a network slice cannot meet them due to        its network conditions, the PC_NSS can select a different        network slice.

By implementing exemplary methods and apparatus disclosed herein, thenetwork operator is able to implement new and complex use cases thatdepend on dynamic modification of the set of network slices that can beassigned alternatively or simultaneously to a UE. Moreover, methods andapparatus disclosed herein are enablers for the more dynamic creationand deployment of network slices, since that availability of a newnetwork slice (or the removal of availability of an old network slice)for the UE can be simplified to the configuration of a network selectionpolicy in the PC_NSS.

The PC_NSS, in order to make decisions about the network slice to selectfor a UE, may be configured to gather UE data from one or more of: aSubscription Database (for example, UE data such as subscribedservices); an MMF (or AMF), i.e. MMF input information (for example,location of the UE, type of UE request originating from the UE (forexample, attach or PDU session establishment) and a UE requested input);a fifth generation (5G) PCRF (for example, if the UE is using a detectedservice, for which the service data usage been surpassed by the UE); andan Analytics function (for example, high signalling load, bad Quality ofExperience, QoE, (high latency) etc.).

The PC_NSS may alternatively or in addition access up to date networkdata about network slice attributes, such as the service that thenetwork slice is intended to deliver, business purpose/customer that thenetwork slice is serving, and the network slice status (for example,load on the network slice, current latency in the network slice todeliver the intended service and message loss within the network slice).

The PC_NSS may combine the collected UE data and/or network data withother parameters, such as time of day and other operator conditions,into selection data for network slice selection.

The selection data for network slice selection results in thedetermination of a network slice or a set of network slices alternatelyor simultaneously available for the UE for this request.

The PC_NSS may provide a selected network slice(s), i.e. one or moreassignable network slice, and the PC_NSS may transmit for each networkslice the corresponding NSRR, which includes the NFs (or a chain ofselected NFs, for example, the SMF and UPF) to route the specific UEinitiated procedure. The NSRR may also include one or more events and/orconditions that would trigger a new network slice selection request. TheNSRR may also include the service scope at which the network sliceapplies.

if the selected network slice does not match the network slice the UE ison and it is not handled by an AMF, the AMF will reroute thecorresponding procedure to the selected network slice. When the selectednetwork slice does not match the network slice the UE is on and theselected network slice is handled by the AMF, the AMF will enforce thenetwork slice information, i.e. the NSRR for the selected network slice.

In exemplary arrangements, if network slicing applies, the PC_NSS mayonly provide an assignable network slice and corresponding NSRRinformation to the AMF when the AMF is in charge of the assignablenetwork slice. Otherwise, the PC_NSS may provide redirect information tothe AMF for it to redirect the initial attach request to a further AMFvia the RAN or via direct signalling between the initial AMF and thefurther AMF.

In exemplary arrangements, the PC_NSS may check (for example in step 514of FIG. 5, described below) whether an NSSAI determined by the PC_NSSmatches the NSSAI provided by the UE. If not and if the determined NSSAIis not supported by the AMF, the PC_NSS may provide redirect informationinstead of network slice information.

The NSRR includes network slice information to be delivered by thePC_NSS to the requesting NF (for example an MMF/AMF, or an SMF). TheNSRR may include one or more of: the network slice instance ID to whichit relates; the service scope at which the network slice applies to (forexample, any service, any service in a PDN, a Service Data Flow in aPDN); the set of NFs forming the network slice (for example, common andspecific to the slice) and through which to route the UE initiatedprocedure; and one or more selection events and/or conditions thattrigger a network slice reselection (per NF, for example in the MMF, arule may be installed to request network slice selection at PDNconnection request, or in the SMF a rule may be installed to requestnetwork slice selection (for further UP selection) at reception of thePDN connection request).

FIG. 3 shows a schematic representation of a network node forimplementing an MMF/AMF 300. The MMF/AMF 300 may be an MMF/AMF 104 ofFIG. 1. The MMF/AMF 300 comprises a transmitter 302 and a receiver 304.The transmitter 302 and receiver 304 may be in data communication withother network entities in a telecommunications network and areconfigured to transmit and receive data accordingly.

The MMF/AMF 300 further comprises a memory 306 and a processor 308. Thememory 306 may comprise a non-volatile memory and/or a volatile memory.The memory 306 may have a computer program 310 stored therein. Thecomputer program 310 may be configured to undertake the methodsdisclosed herein. The computer program 310 may be loaded in the memory306 from a non-transitory computer readable medium 312, on which thecomputer program is stored. The processor 308 is configured to undertakeone or more of the functions of a profile manager 314, a network slicerequester 316 and a network slice manager 318, as set out below.

Each of the transmitter 302 and receiver 304, memory 306, processor 308,profile manager 314, network slice requester 316 and network slicemanager 318 is in data communication with the other features 302, 304,306, 308, 310, 314, 316, 318 of the MMF/AMF 300. The MMF/AMF 300 can beimplemented as a combination of computer hardware and software. Inparticular, the profile manager 314, network slice requester 316 andnetwork slice manager 318 may be implemented as software configured torun on the processor 308, or as combinations of hardware and software inseparate modules. The memory 306 stores the various programs/executablefiles that are implemented by a processor 308, and also provides astorage unit for any required data. The programs/executable files storedin the memory 306, and implemented by the processor 308, can include theprofile manager 314, network slice requester 316 and network slicemanager 318, but are not limited to such.

FIG. 4 shows a schematic representation of a network node forimplementing a PC_NSS 400. The PC_NSS 400 may be a Policy ControlFunction, PCF, 108 controlling slice selection policies in anarchitecture of FIG. 1. The PC_NSS 400 comprises a transmitter 402 and areceiver 404. The transmitter 402 and receiver 404 may be in datacommunication with other network entities in a telecommunicationsnetwork and are configured to transmit and receive data accordingly.

The PC_NSS 400 further comprises a memory 406 and a processor 408. Thememory 406 may comprise a non-volatile memory and/or a volatile memory.The memory 406 may have a computer program 410 stored therein. Thecomputer program 410 may be configured to undertake the methodsdisclosed herein. The computer program 410 may be loaded in the memory406 from a non-transitory computer readable medium 412, on which thecomputer program is stored. The processor 408 is configured to undertakeone or more of the functions of a network slice selector 414 and aselection data manager 416, as set out below.

Each of the transmitter 402 and receiver 404, memory 406, processor 408,network slice selector 414 and selection data manager 416 is in datacommunication with the other features 402, 404, 406, 408, 410, 414, 416of the PC_NSS 400. The PC_NSS 400 can be implemented as a combination ofcomputer hardware and software. In particular, the network sliceselector 414 and selection data manager 416 may be implemented assoftware configured to run on the processor 408, or as combinations ofhardware and software in separate modules. The memory 406 stores thevarious programs/executable files that are implemented by a processor408, and also provides a storage unit for any required data. Theprograms/executable files stored in the memory 406, and implemented bythe processor 408, can include the network slice selector 414 andselection data manager 416, but are not limited to such.

FIG. 5 is a signalling diagram showing an exemplary method fordetermining a network slice for a UE. An exemplary signalling flow willbe described with reference to FIGS. 1, 3, 4 and 5.

-   -   500: The UE 100 transmits a UE request, in this case a        registration request such as a request for connectivity, to the        Radio Access Network (RAN) 102. In an exemplary arrangement, the        UE 100 may transmit along with the UE request, data providing        information to the network for selecting a network slice. For        example, the UE 100 may transmit Network Slice Selection        Assistance Information (NSSAI).    -   502: The RAN 102 receives the request from the UE 100 and        determines a Core Network instance for the UE 100 based on        information provided in the request. In an exemplary        arrangement, the RAN 102 selects the Core Network instance based        on the NSSAI provided by the UE 100 in the request. If the UE        100 does not provide any NSSAI, the RAN 102 may select a default        CN instance.    -   504: The RAN 102 forwards the UE request for connectivity to the        AMF 104 of the selected CN instance, including the NSSAI when        provided by the UE 100.    -   506: The receiver 304 of the AMF 104 receives the UE request        from the RAN 102. In an exemplary arrangement, the profile        manager 314 controls the transmitter 302 to transmit to a        Subscriber Data Management (SDM) 106 function a profile request        for a subscriber profile relating to the user of the UE 100.    -   508: In this exemplary arrangement, the SDM 106, in response to        receiving the profile request, transmits a subscription profile        to the AMF 104. The subscription profile includes a usage type        for the UE 100.    -   510: The AMF 104 may use the retrieved subscription profile from        the SDM 106 in combination with the NSSAI provided by the UE 100        to statically determine a selected network slice to assign to        the UE 100. Alternatively, e.g. if static information is not        enough, the network slice requester 316 of the AMF 104 controls        the transmitter 302 to transmit a network slice selection        request to the PC_NSS 108.        -   If local information stored on the AMF 104 indicates that            the AMF 104 belongs to a deployed solution where dynamic            slice selection is supported, the AMF 104 may transmit the            network slice selection request to the PC_NSS 108 for one or            more authorized network slices that may be assigned to the            UE 100.    -   512: The receiver 404 of the PC_NSS 108 receives the network        slice selection request and the network slice selector 414        selects one or more network slices that are assignable to the UE        100 based on selection data, which may comprise UE data and/or        network data.        -   The UE data may comprise UE specific parameters affecting            network slice selection. In exemplary arrangements, the            selection data is determined by the selection data manager            416 of the PC_NSS 108. The selection data manager 416 may            control the transmitter 402 to transmit one or more UE data            requests to one or more network nodes. The UE data requests            may request UE data from any one of: the SDM 106 (e.g. UE            data such as subscribed services for the user of the UE);            and an analytics system (e.g. UE data such as high signaling            load, bad QoE (high latency)). UE data may also be retrieved            by the selection data manager 416 from data received by the            AMF 104 without the need to request it (e.g. UE data such as            UE location, type of UE request (e.g. attach, PDU session            establishment) and UE requested input).        -   The selection data manager 416 may also obtain network data,            as discussed above.    -   514: Based on the selection data, which may include the UE data        (requested or otherwise received), the network data and/or one        or more other conditions (e.g. time of day or other operator        conditions), the network slice selector 414 of the PC_NSS 108        determines network slice data, which may be an authorized NSSAI,        for the UE 100. If the NSSAI provided by the AMF 104 in the        network slice request, e.g. a UE-provided NSSAI, is valid, the        PC_NSS 108 may also select one or more network slices for the UE        based on the selection data. The network slice selector 414        determines network slice routing data, which may be a NSRR, for        each of the selected network slices.    -   516: The transmitter 402 of the PC_NSS 108 transmits to the AMF        104 the authorized NSSAI and the NSRR(s). Each NSRR may comprise        one or more of the following: the network slice instance ID to        which it relates; the set of NFs forming the network slice and        through which to route a UE request; the selection conditions        and/or events that may trigger a request for network slice        selection to the PC_NSS 108 by each of the network functions        specified in the route above. In exemplary arrangements, the        list of events may specify that the AMF 104 should send a        network slice request to the PC_NSS 108 upon specific mobility        events or upon PDN session establishment, or may for example        specify that the SMF 110 should contact the PC_NSS 108 upon        detection of a specific service data flow; and the service scope        at which the network slice applies, such as for instance, any        service, any service in a PDN, a Service Data Flow in a PDN,        etc.        -   If the NSSAI provided by the AMF 104, e.g. the UE-provided            NSSAI, in the network slice request is not valid, the NSSAI            determiner 418 of the PC_NSS 108 rejects the current slice            selection and transmits to the AMF 104 the authorized NSSAI.    -   518: The receiver 304 of the AMF 104 receives the authorized        NSSAI and NSRR(s) from the PC_NSS 108 and the network slice        manager 318 controls the assignment of network slices to the UE        based thereon. That is, the AMF 104 enforces the decision from        the PCC_NSS 108 with regards to network slice selection.        -   If the authorized NSSAI received from the PC_NSS 108 matches            the NSSAI provided by the UE 100, the network slice manager            318 is able to assign the UE-provided network slice for the            UE 100 and enforces the applicable NSRR received from the            PC_NSS 108        -   If the authorized NSSAI does not match the NSSAI provided by            the UE, the network slice manager 318 determines whether the            authorized NSSAI is supported at the AMF 104 and, if not,            controls the transmitter 302 to transmit the UE request            toward another AMF        -   If the authorized NSSAI does not match the UE-provided NSSAI            and the network slice manager 318 determines that the            authorized NSSAI is supported at the AMF 104, the network            slice manager 318 is able to assign the PC_NSS 108 selected            network slice to the UE 100 based on the authorized NSSAI            and NSRR    -   520: The authentication process for the UE 100 may now be        executed, according to conventional procedures. Note that in        case of UE redirection to the authorized NSSAI, the        authentication process may not be executed.    -   522: In the example of FIG. 5, the connectivity request is        accepted after successful authentication. In an embodiment, the        AMF 104 may provide the UE 100 with updated NSSAI information,        i.e. the authorized NSSAI, if the PC_NSS 108 selected network        slice has been assigned to the UE 100.

In certain exemplary arrangements, the network slice selector 414 of thePC_NSS 108 may check in step 514, for example, whether the determinedNSSAI matches the NSSAI provided by the UE 100. If not, and thedetermined NSSAI is not supported by the AMF 104, the network sliceselector 414 may transmit redirect information to the AMF 104 instead ofthe NSSAI and NSRR. In that case the AMF 104 redirects the UE requesttowards a further AMF based on the redirect information received fromthe PC_NSS 108. The redirect can be done via the RAN 102 or via directsignalling towards the further AMF.

Once the network grants connectivity for the UE 100, PDU sessions may beestablished with the network so that the UE can utilise subscribedservices. FIG. 6 shows a signalling diagram for an exemplary PDU sessionestablishment.

-   -   600: The UE 100 transmits to the AMF 104 a UE request, in this        case a request for the establishment of a PDU Session. The UE        request comprises data identifying the network for which the PDU        session is requested (e.g. APN).    -   602: The receiver 304 receives the UE request (in this case a        PDU Session establishment request). The network slice manager        318 retrieves the selected network slice for the UE 100, as        selected by the PC_NSS 108. The network slice manager 318        determines the corresponding NSRR and any conditions and/or        events included in the NSRR received from the PC_NSS 108 during        the connectivity procedure for the UE 100 (see FIG. 5). The        network slice manager 318 then determines whether any of the        conditions and/or events indicated in the corresponding NSRR has        occurred.        -   If not, the network slice manager 318 controls the            transmitter 302 to transmit the PDU session establishment            request towards the SMF 110 indicated by the corresponding            NSRR, as described in 610 below.        -   If one of the conditions and/or events has occurred, the            network slice manager 318 controls the transmitter 302 to            transmit a network slice selection request to the PC_NSS            108. The network slice selection request includes data            relating to the PDU session establishment request, such as            PDN Identification data.    -   604: The receiver 404 of the PC_NSS 108 receives the network        slice selection request and the network slice selector 414        selects, based on the selection data and the data relating to        the PDU session establishment request, one or more network        slices that may be assigned to the UE 100. This may be done        using the selection data manager in a similar way to that        described above in respect of FIG. 5.    -   606: The network slice selector 414 determines an authorized        NSSAI for the one or more authorized network slices and one or        more corresponding NSRRs, as set out above.    -   608: The network slice selector 414 controls the transmitter 402        to transmit towards the AMF 104, the authorized NSSAI and the        one or more NSRRs.    -   610: The network slice manager 318 of the AMF 104 enforces the        authorized NSSAI and corresponding NSRR(s) received from the        PCC_NSS 108. This may be done as follows.        -   If the network slice manager 318 determines that the            received NSSAI is supported by the AMF 104, it controls the            transmitter 302 to transmit the PDU session establishment            request towards the SMF 110 indicated by the corresponding            NSRR.        -   If the network slice manager 318 determines that the            received NSSAI is not supported by the AMF 104, it controls            the transmitter 302 to transmit the PDU session            establishment request toward another AMF for control of            network slice assignment.        -   If the network slice manager 318 determines that the            received NSSAI does not match the NSSAI selected during the            attach procedure, it controls the transmitter 302 to            transmit to the UE 100 updated NSSAI information.    -   In the case that the PDU session establishment request is to be        handled by the AMF 104, the network slice manager 316 controls        the transmitter to transmit the PDU session establishment        request to the SMF 110 instance indicated by the applicable        NSRR, and may convey also information about the User Plane        Function (UPF) to select.    -   The AMF 104 may also forward to the SMF 110 data identifying the        events and/or conditions that would trigger a network slice        reselection, which are included in the NSRR(s). For example, if        the NSRR indicates network slice reselection at service data        flow detection, the AMF 104 may forward this data to the SMF        110. The SMF 110 then, at the reception of the PDU Session        establishment request, may query the PC_NSS 108 for network        slice selection. At request from the SMF 110, the PC_NSS 108        could install the conditions for a service data flow to be        routed via one network slice (UP) or another. (This step is not        shown in the flow).    -   612: The SMF 110 transmits a query to the NG Policy Function (NG        PF) to obtain policy decisions applicable to the PDU session        regarding QoS applicable to the session, charging applicable to        the session. The NG PF transmits a response including the policy        decisions for the session. In particular, the NG PF might be        implemented in the same network node as the PC_NSS or in a        different network node.    -   614: The SMF 110 receives the policy decisions from the NG PF        and, once the PDU session is authorized by the NG PF, the SMF        110 transmits to the AMF 104 a notification that it accepts the        PDU session establishment request.    -   616: The AMF 104 receives the notification and transmits to the        UE 100 a corresponding notification accepting the PDU session        establishment request.

Exemplary methods and apparatus disclosed herein propose a mechanismimplemented in a core network node for use as a PC_NSS that extendsnetwork slice selection functionality so that:

-   -   To decide about the network slice to assign to a UE 100, the        PC_NSS 108 accesses to up to date network slice information        about applicable attributes, such as the service that the        network slice is intended to deliver, the business        purpose/customer that the network slice is serving, and the        network slice status (e.g. load, current latency to deliver the        intended service, message loss etc.).    -   To instruct the core network node about how to route access or        PDU session establishment requests in a selected network slice,        the PC_NSS returns to the requesting network function (AMF/MMF        104, SMF 110) a NSRR, containing.        -   the network slice instance ID to which it relates,        -   the service scope at which the network slice applies (any            service, any service in a PDN, a Service Data Flow in a            PDN),        -   the set of NFs (common and specific for the slice) to route            PDU session establishment requests, and        -   the events that trigger a Network Slice reselection per NF            specified in the route above. For example, in the AMF 104 it            can be installed a rule to request network slice selection            at PDN connection request, or in the SMF 110 it can be            installed a rule to request network slice selection (for            further UP specific NF selection) at reception of the PDN            connection request, etc

The mechanism is based on:

-   -   PC_NSS, at Policy decision request from the AMF, and based on        dynamic policies, may decide the authorized Network Slice that        can be assigned for the UE at attach. If the authorized Network        Slice does not correspond with the one provided by the UE (the        network slice(s) provided by the UE is derived by the PC_NSS        from the Network Slice Selection Assistance Information (NSSAI)        provided by the UE), and the authorized network slice does not        comprise, as NFs, the AMF requesting policy decision, the PC_NSS        may indicate the AMF that the UE is redirected to the proper        Network Slice, and may provide the authorized NSSAI. The AMF may        inform the UE about the authorized NSSAI.    -   When the authorized Network Slice corresponds to the one derived        from the NSSAI provided by the UE, or the requesting AMF is a        network function included into the authorized network slice(s),        the PC_NSS can provide to the AMF at UE attach the information        about the NSRR(s) (multiple NSRRs when the UE can simultaneously        attach to several slices).    -   At PDU session establishment, the AMF may apply the NSRR(s) and        at service scope matching, it may either contact the PC_NSS (if        NSRR defined conditions and/or events for AMF to do so) or it        may contact the SMF as indicated by the set of NFs in the NSRR.        When forwarding the PDU session establishment to the SMF, the        AMF may also include information about whether the SMF has to        contact the PC_NSS upon PDU session establishment.    -   The SMF may contact the PC_NSS at PDU session establishment if        the AMF indicated so. The PC_NSS can provide to the SMF        information about the NSRR to be applied for that network slice        to use at service (data flow) procedures. This decision may be        based on dynamic polices that consider different network and        subscriber conditions. The PC_NSS can also provide additional        information to the SMF that indicates under which conditions a        network slice reselection needs to be triggered for.    -   The SMF or the AMF may contact the PC_NSS at other events than        attach/connectivity request or PDU session establishment (such        as mobility, change of access type, service detection, etc.), if        configured to do so within the NSRR. The PC_NSS may then select        a different network slice and/or provide a new NSRR. This        enables use cases where the operator applies a different network        slice for different geographical areas, for different access        networks or when a new service is activated for this PDN        connection.    -   The PC_NSS can modify or revoke any of the previously provided        NSRR at any moment.    -   The PC_NSS can interface the Analytics function, and react at        Analytics insights (as e.g. congested area, terminal        malfunctioning . . . ). The PC_NSS can interface with an        Analytics function that provide the PC_NSS with analytics        insights (e.g. network slice conditions) to be considered in the        network slice selection process. If a user starts a service that        requires specific latency requirements and a network slice        cannot meet them due to its network conditions, the PC_NSS can        select a different network slice.

A computer program may be configured to provide any of the abovedescribed methods. The computer program may be provided on a computerreadable medium. The computer program may be a computer program product.The product may comprise a non-transitory computer usable storagemedium. The computer program product may have computer-readable programcode embodied in the medium configured to perform the method. Thecomputer program product may be configured to cause at least oneprocessor to perform some or all of the method.

Various methods and apparatus are described herein with reference toblock diagrams or flowchart illustrations of computer-implementedmethods, apparatus (systems and/or devices) and/or computer programproducts. It is understood that a block of the block diagrams and/orflowchart illustrations, and combinations of blocks in the blockdiagrams and/or flowchart illustrations, can be implemented by computerprogram instructions that are performed by one or more computercircuits. These computer program instructions may be provided to aprocessor circuit of a general purpose computer circuit, special purposecomputer circuit, and/or other programmable data processing circuit toproduce a machine, such that the instructions, which execute via theprocessor of the computer and/or other programmable data processingapparatus, transform and control transistors, values stored in memorylocations, and other hardware components within such circuitry toimplement the functions/acts specified in the block diagrams and/orflowchart block or blocks, and thereby create means (functionality)and/or structure for implementing the functions/acts specified in theblock diagrams and/or flowchart block(s).

Computer program instructions may also be stored in a computer-readablemedium that can direct a computer or other programmable data processingapparatus to function in a particular manner, such that the instructionsstored in the computer-readable medium produce an article of manufactureincluding instructions which implement the functions/acts specified inthe block diagrams and/or flowchart block or blocks.

A tangible, non-transitory computer-readable medium may include anelectronic, magnetic, optical, electromagnetic, or semiconductor datastorage system, apparatus, or device. More specific examples of thecomputer-readable medium would include the following: a portablecomputer diskette, a random access memory (RAM) circuit, a read-onlymemory (ROM) circuit, an erasable programmable read-only memory (EPROMor Flash memory) circuit, a portable compact disc read-only memory(CD-ROM), and a portable digital video disc read-only memory(DVD/Blu-ray).

The computer program instructions may also be loaded onto a computerand/or other programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer and/or otherprogrammable apparatus to produce a computer-implemented process suchthat the instructions which execute on the computer or otherprogrammable apparatus provide steps for implementing the functions/actsspecified in the block diagrams and/or flowchart block or blocks.

Accordingly, the invention may be embodied in hardware and/or insoftware (including firmware, resident software, micro-code, etc.) thatruns on a processor, which may collectively be referred to as“circuitry,” “a module” or variants thereof.

It should also be noted that in some alternate implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved. Moreover, the functionality of a given block of the flowchartsand/or block diagrams may be separated into multiple blocks and/or thefunctionality of two or more blocks of the flowcharts and/or blockdiagrams may be at least partially integrated. Finally, other blocks maybe added/inserted between the blocks that are illustrated.

The skilled person will be able to envisage other embodiments withoutdeparting from the scope of the appended claims.

The invention claimed is:
 1. A network node configured for use as aPolicy Control Network Selection function, PC_NSS, of atelecommunications network, the PC_NSS for selecting one or more networkslices assignable for a UE within the telecommunications network, thenetwork node comprising: a receiver configured to receive a networkslice selection request from an Access and Mobility Management Function,AMF; a selection data manager configured to determine selection dataspecifying at least one UE specific parameter affecting network sliceselection; a network slice selector configured to select a network sliceassignable for the UE, based on the selection data, and to determinenetwork slice data identifying the assignable network slice and acorresponding network slice routing rule identifying the assignablenetwork slice and a set of network functions forming the assignablenetwork slice; and the network slice selector being further configuredto control a transmitter to transmit to the AMF the network slice dataand the corresponding network slice routing rule for controllingassignment of a network slice for the UE based on the network slice dataand network slice routing rule.
 2. The network node according to claim1, wherein the network slice data transmitted via the transmittercomprises an authorized network slice selection assistance information,NSSAI, representing at least one assignable network slice for the UE,and respectively corresponding at least one network slice routing rule.3. The network node according to claim 1, wherein each network slicerouting rule further comprises a service scope at which the assignablenetwork slide applies, wherein the service scope indicates any one of: aservice, a service in a packet data network, PDN, and a service dataflow in a PDN.
 4. The network node according to claim 1, wherein thenetwork slice routing rule further comprises data indicating at leastone of: at least one condition; and events specifying when a furthernetwork slice selection request should be transmitted to the PC_NSS. 5.The network node according to claim 1, wherein the network sliceselector is further configured to control the transmitter to transmit tothe AMF redirect data for redirecting assignment of the network slicefor the UE to a further AMF, and the network slice selector isconfigured to determine the redirect data based on whether theassignable network slice is supported by the further AMF.
 6. The networknode according to claim 1, wherein the selection data manager isconfigured to determine at least part of the selection data bycontrolling the transmitter to transmit at least one selection datarequest to at least one further network node in the telecommunicationsnetwork, and the receiver is configured to receive the selection datafrom the at least one further network node.
 7. The network nodeaccording to claim 1, wherein the selection data further comprises atleast one of: network slice data comprising at least one network sliceattribute affecting network slice selection; a time of day; and at leastone network operator specified condition.
 8. A method for controlling anetwork node configured for use as a Policy Control Network Selectionfunction, PC_NSS, of a telecommunications network, the PC_NSS forselecting one or more network slices assignable for a UE within thetelecommunications network, the method comprising: receiving, by areceiver, a network slice selection request from an Access and MobilityManagement Function, AMF; determining, by a selection data manager,selection data specifying at least one UE specific parameter affectingnetwork slice selection; selecting, by a network slice selector, anetwork slice assignable for the UE, based on the selection data, anddetermining, by the network slice selector, network slice dataidentifying the assignable network slice and a corresponding networkslice routing rule identifying the assignable network slice and a set ofnetwork functions forming the assignable network slice; and controllinga transmitter, by the network slice selector, to transmit to the AMF thenetwork slice data and the corresponding network slice routing rule forcontrolling assignment of a network slice for the UE based on thenetwork slice data and network slice routing rule.